At what point is it safe to stop wit' da Bondo and assume a surfacer primer will do the rest?

I'm working on the 8ft long bedside of my 65 F250 with a recently acquired long board and thankfully, because of it, I've found some minor rippling that no doubt would have showed up in the final finish. That led me to laying straightedges along side it and using feeler guages to measure with I've determined the biggest deviation I've got is less than 25 thou. Can I fix that much with primer? Figuring each coat for 5-10 thou I'm thinkin' a few fat coats of primer might fill things up. Or should I turn it into the Bondo bed with a full length thin fill?

I'll tell ya, I got so tired of sanding that pink Bondo I went and got me some green just for a scenery change! LOL! But I'll keep the faith. If Bondo's the best ......

Bill

 

My vote would be to go with more bondo. I've driven myself nuts trying to get every little ripple out so they're not visible when looking at the panel edgewise - almost impossible. Using different color bondo is a good idea, it lets you know how much you have sanded off. Primer fills scratches in bondo better than it does ripples, especially the big ones.

When you do get around to priming, after sanding the primer once, try wetting a rag with a weak (slow drying) prep wash, and look at the panel edgewise while it's wet - it will give you an idea how shiny paint will look on it.

 

I am no expert in the area of body work for sure....However, I found that one of the problems that I always had was.....yep...not using enough bondo..I found this out by watching a professional....my thoughts are that you need to cover a whole lot more area than needed...this is how I had my success when working on my old 71....after painted...you can see a few little dings that I missed....but hey....it is 33 years old......lol...!

 

<cr>
I don't know if you did it but doing a final skim coat of filler, well extending past the edges of your work area, will help flatten things out. For my skim coat, I usual use a polyester filler, which is finer.

Another thing you can do is make a longer, long board. Some people I've known have used a 5' long board. Of course, you have to use self-stick sandpaper.

Changing the angle of your light source can help find areas that need additional work. Shining a flashlight down the length of the box can help pick up problem areas.

Run your hand down the side, using your entire palm, not your finger tips. Close your eyes while doing it. Some put on thin cotton glove. Be one with the metal and listen to what your hand is telling you. Wowser. That almost sounds like some kind of Zen thing, doesn't it?

Remember, if you even think you can feel a defect, you have a defect.

Paint doesn't hide anything. It only helps show a problem area.

I know this wasn't really what you were asking. I only mentioned it because others might be reading along.

 

When you get really creative, you will add a little blue hardener with red hardener to try to get a purple color, or maybe a little yellow hardener and blue to get a bright green. Bees seem to love body filler dust, and I am allergic to them, so it makes bodywork fun sometimes in the summer. Just block your filler well, and go over it till it feels pretty straight. I sometimes sand in an x patern, but experience is the best way to know when its straight. A lot of people sand to much filler off. It should blend in well and past the edge of the repair. Its easier to put a skim coat over the hole repair area, then just to bondo a part of the repair that needs extra filler.Don't sand your filler with too fine of a grit, it is easier to get straight with a coarser grit. I only get my filler down to 80 grit before putting on primer surfacer, but some go finer. As long as its fairly straight, A good filler primer surfacer will take care of small stuff, along with guide coating, blocking with like 180 grit, repriming, blocking again. Prime and block as many times as you feel it needs to be nice and straight, and there is no guide coat left when you block. Sand the final coat of primer with the grit recommended for the paint you are spraying.

 

this point takes alot of sanding. you bondo them sand and prime them you take some black paint and just mist it over them primer or bondo. sand by hand and it will help you to know when everything is smooth and straight. if you have some low spots yo might have to add more bondo and them parime and sand all over till you get it smooth.

 

Well thanks for all the reponses guys and yeah, we have identified a definite tendency to sand off too much of the bondo!

Aekisu, can you tell me more about the polyester filler? So far I've used the standard pink Bondo brand and the green stuff from NAPA, but I caught an episode of CCR on the Speed Channel where they finished off with some kinda 2-part putty for pinholes and other minor issues. No info on what it actually was tho. That show's mostly a lotta loud rock and roll music with wild camera angles lightly interspresed with useful tips. MTV on wheels.

Better than MTV's "Pimp My Ride" tho. LOL! That show's ridiculous.

 

<cr>
I use 2 different products. One is called Metal Glaze by Evercoat. It comes in a squeeze bottle and is a 2-part filler. It is fairly fluid and is great for taking care of pinholes and the like. I don't use it a lot.

The second product is called Putty Cote. It is also a 2-part filler. It is what I use to make a final skim coat. Very fine grained and easy sanding. Helps eliminate the need for multiple coats of primer that flatten out the panel.

 

The best way i have found is to lightly mist the surface with a can of black spray paint. Then when you flat board you sand the specks of black paint of on the high spots and not on the lows. This works great for me.

 

A trick that I picked upl.....(speaking of body work)...is to use a can of spray paint, preferably black....mist the repaired areas and then lightly sand...this gives you an idea of the low places...consequently you can tell if you are finished....! Worked for me.......!

 

Dang Bajha...what was I thinking....didn't mean to repeat what you had just said......old age is getting to me.....I guess it worked for both of us....so
it has to be right........!

 

I was wondering if there is anything that can be added to Bondo similar to the way you add water to joint compound when doing drywall? It'd make it easier to do a skim coat that way. On my project the bed is in horrendous shape and every repair is being done with Bondo and tape as I don't have a garage and am working on it outside, welding not an option. Think a good skim coat might be needed along the bed. Maybe I'll check that Putty-Cote out.

-Ray

 

About 15 years ago my jobber had stuff called "plastic honey". (I think that was it) That's what it was for - to thin body filler for skim coating. It worked great, but it was discontinued according to my jobber. The Evercoat product that Aekisu described took it's place well, but is costly, compared to standard filler.

 

I read somewhere that you can use fiberglass resin to thin Bondo.